Multicolor hyperafterglow from isolated fluorescence chromophores

High-efficiency narrowband emission is always in the central role of organic optoelectronic display applications. However, the development of organic afterglow materials with sufficient color purity and high quantum efficiency for hyperafterglow is still great challenging due to the large structural relaxation and severe non-radiative decay of triplet excitons. Here we demonstrate a simple yet efficient strategy to achieve hyperafterglow emission through sensitizing and stabilizing isolated fluorescence chromophores by integrating multi-resonance fluorescence chromophores into afterglow host in a single-component copolymer. Bright multicolor hyperafterglow with maximum photoluminescent efficiencies of 88.9%, minimum full-width at half-maximums (FWHMs) of 38 nm and ultralong lifetimes of 1.64 s under ambient conditions are achieved. With this facilely designed polymer, a large-area hyperafterglow display panel was fabricated. By virtue of narrow emission band and high luminescent efficiency, the hyperafterglow presents a significant technological advance in developing highly efficient organic afterglow materials and extends the domain to new applications.


Synthesis of 7-bromoquinolino[3,2,1-de]acridine-5,9-dione (3)
Two drops of N,N-dimethylformamide (DMF) was added to the mixture of 5-bromo-2-(diphenylamino)isophthalic acid (2) (2.60 g, 6.31 mmol) in dry DCM (100 mL) under an argon atmosphere. After adding oxalyl chloride (1.18 mL, 13.88 mmol), the mixture was refluxed for 30 minutes. And then, the Tin(IV) chloride DCM solution (6.94 mL, 2 M, 13.88 mmol) was added and the mixture was refluxed for 3 h. After cooling to room temperature, the mixture was added dropwise to a 1 M aqueous solution of sodium hydroxide and extracted with DCM three times. The organic layer was dried over anhydrous magnesium sulfate. After filtration and solvent evaporation, the given residue was purified through silica gel column chromatography using DCM/PE (V/V: 3/1) as eluent to give the product as an orange-yellow solid product (Yield: S5 1.71 g, 72%). 1
In argon atmosphere, 0.01 equivalent (eq) of 2,2'-azobis(2-methylpropionitrile) (AIBN) and 1.0 eq of vinyl derivative were dissolved in 25 mL freshly distilled tetrahydrofuran (THF). The S9 mixture was heated to 55℃ for 16 h, during which the white, green or red solid was constantly precipitated out from solution. Then, the mixture was cooled to room temperature and added into methanol to precipitate polymeric materials, then the crude product was filtered, followed by washing with PE and DCM, acetone in sequence. Then the solid was dissolved in deionized water and dialyzed by a dialysis tube (molecular weight cut-off = 1000) for 72 h. Polyacrylamide (PAM). Following the general procedure of radical polymerization using acrylamide (3.55 g, 50.0 mmol, 100 eq), and appropriate amount of AIBN (82.00 mg, 0.5 mmol, 1 eq) in 25 mL freshly distilled THF to afford 3.30 g white powder polymer with a yield of 92.9%.  Firstly, 0.6 g PAMQAx powder was dissolved in 10 mL deionized water followed by the sonication for 10 min under ambient conditions. Subsequently, the mixture was intensely stirred at 60℃ for 1 h to obtain the transparent aqueous solution. Finally, the well-dissolved solution was poured into a clean petri dish and dried at 70℃ in an oven to prepare the amorphous polymer film. S15

Photophysical and morphology investigations
Ultraviolet/visible (UV/Vis) and fluorescence spectra were recorded on a Jasco V-750 spectrophotometer and Edinburgh FLS980, respectively. The absolute photoluminescence quantum yield (PLQY) was obtained using an Edinburgh Where Bi and τi represent the amplitudes and lifetimes of the individual components for multi-exponential decay profiles, respectively.
The average lifetime was calculated by the function of where φi is the amplitude fraction.
To get the intensity-averaged lifetime (τint), the φi int is defined by the function of To get the amplitude averaged lifetime (τamp) which was used for the analyses of FRET S16 process, the φi amp is defined by the function of: τamp is achieved by the function of:

Hyperafterglow LED and displays
Fabrication and measurements of hyperafterglow LED devices: In a general procedure, PAMQA3 was dissolved in a water solution (100 mg/mL) and then the PAMQA3 solution was coated on a self-designed lampshade. Then the lampshade with PAMQA3 film was assembled with a UV LED chip (285 nm) for fabricating the prototype hyperafterglow LED. The devices without encapsulation were measured immediately after fabrication under ambient atmosphere at room temperature. Steady-state electroluminescent (EL) spectra of the devices were measured by a PR655 spectra scan spectrometer and delayed EL (10 ms) spectra of the devices were measured using an Edinburgh FLS980 fluorescence spectrophotometer. The luminance-voltage and current-voltage characteristics were recorded using an optical power meter and a Keithley 2602 voltage current source.
Detailed procedure for the fabrication of hyperafterglow display panel: 5 g PAMQA3 powders were dissolved in 15 mL deionized water, followed by the sonication for 30 mins under ambient conditions. Subsequently, the mixture was vigorously stirred at 60°C for 1 hour to obtain the transparent solution. Last, the well-mixed solution was poured into a clean teflon box, followed by natural evaporation of water. The large and uniform polymer film could be easily achieved for display applications.